degree Fahrenheit hour/Btu (th) Unit Converter

Definition of degree Fahrenheit hour/Btu (th) unit

The degree Fahrenheit hour per British thermal unit (thermochemical), written °F·h/Btu(th), measures thermal resistance: the temperature difference in degrees Fahrenheit required to sustain heat flow of one thermochemical Btu per hour. Larger values indicate better insulation.

History of degree Fahrenheit hour/Btu (th) unit

Thermal-resistance measures developed alongside nineteenth-century studies of conduction, insulation, and steam engineering, when British thermal units and Fahrenheit temperature differences were common in industry. The hour-based form became convenient for building and furnace calculations because heating loads were often expressed as Btu per hour. The thermochemical qualification distinguishes this unit from versions using other Btu definitions. Thermochemical Btu practice rests on the calorie fixed at 4.184 joules, making one Btu(th) equal to approximately 1,054.35 joules. Today, SI units are preferred, but this unit remains recognizable in North American engineering.

Applications of degree Fahrenheit hour/Btu (th) unit

Engineers use °F·h/Btu(th) to rate insulation assemblies, walls, roofs, windows, furnaces, refrigeration equipment, and piping in customary-unit calculations. For example, a component rated 20 °F·h/Btu(th) permits only 1 Btu(th) per hour of heat transfer when its two sides differ by 20 °F. Designers can combine layer resistances while specifications increasingly convert results to m²·K/W.

Complete list of degree Fahrenheit hour/Btu (th) unit conversion